Update audio_processing module

Corresponds to upstream commit 524e9b043e7e86fd72353b987c9d5f6a1ebf83e1

Update notes:

 * Pull in third party license file

 * Replace .gypi files with BUILD.gn to keep track of what changes
   upstream

 * Bunch of new filse pulled in as dependencies

 * Won't build yet due to changes needed on top of these

webrtc/system_wrappers/source/event_timer_posix.h

@@ -0,0 +1,60 @@
+/*
+ *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_SYSTEM_WRAPPERS_SOURCE_EVENT_POSIX_H_
+#define WEBRTC_SYSTEM_WRAPPERS_SOURCE_EVENT_POSIX_H_
+
+#include "webrtc/system_wrappers/interface/event_wrapper.h"
+
+#include <pthread.h>
+#include <time.h>
+
+#include "webrtc/system_wrappers/interface/thread_wrapper.h"
+
+namespace webrtc {
+
+enum State {
+  kUp = 1,
+  kDown = 2
+};
+
+class EventTimerPosix : public EventTimerWrapper {
+ public:
+  EventTimerPosix();
+  ~EventTimerPosix() override;
+
+  EventTypeWrapper Wait(unsigned long max_time) override;
+  bool Set() override;
+
+  bool StartTimer(bool periodic, unsigned long time) override;
+  bool StopTimer() override;
+
+ private:
+  static bool Run(void* obj);
+  bool Process();
+  EventTypeWrapper Wait(timespec* end_at);
+
+ private:
+  pthread_cond_t  cond_;
+  pthread_mutex_t mutex_;
+  bool event_set_;
+
+  rtc::scoped_ptr<ThreadWrapper> timer_thread_;
+  rtc::scoped_ptr<EventTimerPosix> timer_event_;
+  timespec       created_at_;
+
+  bool          periodic_;
+  unsigned long time_;  // In ms
+  unsigned long count_;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_SYSTEM_WRAPPERS_SOURCE_EVENT_POSIX_H_